The 'Air Quality Index' score is based on data gathered from the EPA, USGS, and local authorities. Although no city in the US ranked a score of poor or worst, there is
still a wide spectrum of air quality index scores. Please note the score is only an estimate --- weather, the seasons, and local conditions can radically affect the air quality anytime during the year.
Sources: EPA, USGS, and Synergos Technologies, Inc.

Major Air Pollutants

The following chart shows the ranking of the 5 major air pollutants montitored by the EPA. The chart shows the quantity of pollutant
as a percentage to the minimum allowed (before it is considered a serious health risk) by the EPA. It is interesting to note that in
the majority of cases Ozone is the major pollutant facing most cities.
Sources: EPA - Air Quality Trends 2001